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A023814 Number of associative binary operations on an n-set; number of labeled semigroups. 17
1, 1, 8, 113, 3492, 183732, 17061118, 7743056064, 148195347518186, 38447365355811944462 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
LINKS
Alex Bailey, Martin Finn-Sell, and Robert Snocken, Subsemigroup, ideal and congruence growth of free semigroups, arXiv preprint arXiv:1409.2444 [math.GR], 2014.
A. Distler and T. Kelsey, The semigroups of order 9 and their automorphism groups, arXiv preprint arXiv:1301.6023 [math.CO], 2013.
C. Noebauer, Home page [broken link]
Eric Weisstein's World of Mathematics, Semigroup.
CROSSREFS
a(n) + A079172(n) = A002489(n).
Sequence in context: A092084 A346985 A099715 * A217772 A062126 A222520
KEYWORD
nonn,more
AUTHOR
Lyle Ramshaw (ramshaw(AT)pa.dec.com)
EXTENSIONS
a(8), a(9) from Distler and Kelsey (2013). - N. J. A. Sloane, Feb 19 2013
STATUS
approved

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Last modified March 19 03:33 EDT 2024. Contains 370952 sequences. (Running on oeis4.)